Recently, various electrical components are mounted on a vehicle or the like. Such electrical components are connected by a wire-like structure called a wire harness in which a plurality of electric wires or communication lines are bundled by a bundling member such as an insulation lock or a protective member such as a tape. Such a wire harness is designed so as to be laid in a predetermined three-dimensional space, and produced while being developed two-dimensionally on a jig plate.
FIGS. 1(A) and 1(B) are views respectively showing shapes of a wire harness in designing and producing processes. As shown in FIG. 1(A), usually, the wire harness is designed so that it has a plurality of branch wires 1b1 to 1b4 which branch off from a trunk wire 1a in different directions, clamps 2a to 2g and the like are attached to end portions of the wires or an intermediate points (in place of the clamps, grommets may be used or connectors may be attached to the end portions), and the wire harness is laid in a predetermined three-dimensional space such as a door of a vehicle or a floor. However, the wire harness which has been designed under the assumption of a three-dimensional space as described above is produced while being developed on a two-dimensional jig plate as shown in FIG. 1(B). In a developed state, therefore, the branch wires 1b1 to 1b4 which branch off in different directions, and the clamps 2a to 2g produce a twist with respect to the trunk wire 1a. This will be described with reference to FIG. 2.
FIGS. 2(A) and 2(B) are views illustrating a twist angle in a wire harness to which the invention is to be applied. In a state where the trunk wire 1a of the wire harness which has been designed under the assumption of a three-dimensional space is linearly stretched without being twisted as shown in FIG. 2(A), for example, the branch wires 1b1 and 1b2 branch off in different directions by an angle θ as viewed from the front side as shown in FIG. 2(B). Similarly, also two clamps (mainly attached to intermediate portions of the trunk wire) which are not shown in the figures sometimes branch off in different directions by the angle θ as shown in FIG. 2(B). In the case of the clamps, however, the angle θ is an angle formed by straight lines v1, v2 connecting twist application points p1, p2 due to the two clamps and the center axis of the trunk wire 1a, i.e., the two clamp rotation axes as shown in FIGS. 2(A) and 2(B). Moreover, a branch wire and a clamp may possibly form the angle θ in a similar manner.
In a process of producing the wire harness, all the trunk wire, the branch wires, and the clamps constituting the wire harness are developed on a jig plate which is basically a two-dimensional plane. In a process of producing the wire harness, when the trunk wire 1a and the branch wire 1b1 are extended along the jig plate to be set as a reference, therefore, the branch wire 1b2 is twisted by a degree corresponding to the angle θ. In the description, such an angle θ is referred to as the twist angle.
Usually, a trunk wire is thicker than a branch wire. Alternatively, these wires may have the same thickness, or may have inverse thickness relationships. A trunk wire, and a branch wire may be otherwise called, or for example a main wire member and a sub wire member (branch wire member), respectively. In the description, a clamp means a support member for a wire harness, such as a connector or a clip.
As prior art literature information related to the invention of the application, there is the following literature:
[Non-patent Reference 1]
“Matrix finite element method”, B. Nath, Brain Books Publishing Co., Ltd., Aug. 10, 1978, p. 7-15